Power train for amphibian

ABSTRACT

Power train has an engine, transmission, water jet, and sandwich power take off. The power take off output shaft is enclosed by chain case, and drives shaft, which runs below or alongside engine oil sump; or through the sump in a tunnel or recess. A decoupler may be provided in the marine drive. Transfer case transfers drive power from transmission to output shaft, which drives drive shaft and rear wheel differential. Four-wheel drive may be provided, with additional forward drive shaft and differential. A center differential may be provided in or adjacent to the transfer case; transmission may be manual, sequential shift, semi-automatic, automatic, or a continuously variable transmission. The marine drive may be a jet drive, as shown, or a screw propeller, or other marine propulsion means.

The present invention relates to a power train for an amphibious vehicle which power train comprises an engine and in-line transmission, with a power take off positioned between the engine and the in-line transmission of the vehicle and commonly known as a sandwich power take off. The invention also relates to an amphibious vehicle having such a power train.

In an amphibious vehicle it is advantageous to use a power train which an engine and transmission are positioned towards the rear of the vehicle. The weight of the power train is therefore positioned towards the back of the vehicle, which is necessary for good vehicle performance when the vehicle is in marine mode. Furthermore, the position of the power train maximises the space available towards the front of the vehicle for the passenger compartment.

A power train is disclosed for use in amphibious military personnel carrier in U.S. Pat. No. 5,752,862 (Mohler). The disclosed power train uses a rear mounted engine and a combined transmission and differential mounted at the front of the vehicle. Although Mohler uses the drive shafts from the differential to drive caterpillar tracks, such drive shafts could also be used to provide drive to the front road wheels of a civilian amphibious vehicle. However, the power train arrangement disclosed in Mohler has several disadvantages for application to such a civilian vehicle. First, the location of the transmission at the front of the vehicle may reduce passenger and/or luggage space. Secondly, the arrangement requires a propeller shaft running through the passenger area. This shaft, which carries full engine power and rotates at engine speed, takes up valuable passenger space and will generate noise. Third, front wheel drive is not an optimal solution for a rear engined vehicle, as traction will not be as good as if the engine weight is placed over the driven wheels. This can give problems for example in take-off on slippery surfaces, and unusual on-road handling characteristics.

Other power train arrangements for use in an amphibious vehicle are known from U.S. Pat. No. 5,590,617 (Aquastrada) and U.S. Pat. No. 3,765,368 (Asbeck). In these power trains an engine and transmission are connected end-to-end in conventional automotive rear wheel drive fashion, but with the overall arrangement reversed to drive the front wheels. As can be seen particularly clearly from Aquastrada, this forces the passenger seating area towards the front of the vehicle, followed by a long rear deck area which cannot be used for passenger or luggage space.

It is an object of the invention to resolve problems in packaging and traction in the prior art solutions, reducing the lengthwise space taken up by the power train.

In accordance with a first aspect of the invention, there is provided a power train for an amphibious vehicle, which power train comprises an engine, an in-line transmission and a sandwich power take off being positioned between the engine and the transmission, the output from the power take off being adapted to transfer drive to a marine propulsion unit located at the rear of the amphibious vehicle, by means of a shaft which runs below or through the oil sump of the engine, or alongside the engine, characterised in that the output from the transmission is adapted to transfer drive to a differential located at the rear of the amphibious vehicle.

The differential is preferably located rearward of the engine.

In a preferred embodiment of a power train according to the invention, the output from the power take off is in the form of an output shaft which is connected to a drive shaft which runs below or through the oil sump of the engine, or alongside the engine. The oil sump of the engine may have a tunnel or recess through which the drive shaft passes.

In a further preferred embodiment of a power train according to the invention, the power take off is adapted to transfer drive to a marine propulsion unit located substantially in line with the engine and the transmission.

Preferably, the output from the transmission is transferred to the rear differential through a transfer case. In addition to driving the rear differential, the transfer case may also drive a differential located towards the front of the vehicle for driving the front wheels of the vehicle. This arrangement enables a four wheel drive facility when the vehicle is operated in land mode.

A marine drive decoupler may be provided so that drive to the marine propulsion unit can be selectively decoupled.

In accordance with a second aspect of the invention, there is provided an amphibious vehicle having a power train in accordance with the first aspect.

The invention will now be described, by way of example, with reference to the following drawings in which:

FIG. 1 is a side view of a first embodiment of a power train in accordance with the invention, in which drive is provided to the rear wheels only; and

FIG. 2 is a side view of a second embodiment of a power train in accordance with the invention, in which drive is provided to front and rear wheels.

Referring first to FIG. 1, power train 1 comprises an engine 2, a transmission 3, and a water jet 4, the respective centre line of each being located substantially along the centre line of the amphibious vehicle. The transmission may comprise a manual, sequential shift, semi-automatic, or automatic gearbox, or a continuously variable transmission (CVT).

A power take off 5, located between the engine 2 and the transmission 3 has an output shaft 6 driven by engine 2, and is enclosed by a chain case 7. The power take off may be of any suitable type and may, for example, be constructed according to the applicant's co-pending British patent application No. GB0020884.3.

The output shaft 6 of the power take off is coupled to a drive shaft 8 which runs rearward to a marine propulsion unit 4. As shown in FIG. 1, the marine propulsion unit is a water jet, but a screw propeller or any other suitable marine propulsion system may be employed. A decoupler 9 is provided in the drive line from the power take off to the marine propulsion unit so that drive to the marine propulsion unit can be selectively coupled and decoupled. However, such a marine drive decoupler is not essential and can be omitted.

In the embodiment shown in FIG. 1, the drive shaft 8 for the marine propulsion unit runs in a tunnel 11 through the oil-sump12 of the engine 2. Alternatively, the drive shaft may run below the oil-sump or beside the oil-sump, on whichever side of the engine may be convenient, with the marine propulsion unit located accordingly. Tunnel 11 may be fully enclosed as shown, or in the form of a recess in the sump, which recess is open at its base.

The transmission 3 is of a conventional longitudinal type. The drive or output end 18 of the transmission is connected to a transfer case 13 which transfers drive power from the transmission 3 to an output shaft 14. The output shaft 14 is connected by a drive shaft 15 to a differential 16, which is located between the timing end 17 of the engine 2 and the marine propulsion unit 4 at the rear of the vehicle. The differential 16 transmits drive to the rear wheels of the amphibious vehicle via axle shafts in conventional automotive manner.

Although not shown in FIG. 1, the transfer case 13 may comprise a driving sprocket rotatably fast with an output shaft of the transmission, and a driven sprocket rotatably fast with the output shaft 14 of the transfer case 13, drive being transmitted between the two sprockets by means of a chain or belt.

A second embodiment of the invention will now be described with reference to FIG. 2 in which common reference numerals are used to denote parts in common with the embodiment shown in FIG. 1. The power train 10 is essentially the same as the power train 1 shown in FIG. 1, the only difference being that the transfer case 13 also provides drive to the front wheels of the vehicle by means of a forward drive shaft 19 and differential 20. A centre differential (not shown) may also be provided in or adjacent to the transfer case 13. 

1. A power train for an amphibious vehicle, which power train comprises an engine, an in-line transmission and a sandwich power take off positioned between the engine and the transmission, the output from the power take off being adapted to transfer drive to a marine propulsion unit located at the rear of the amphibious vehicle, by means of a shaft which runs below or through the oil sump of the engine, or alongside the engine, characterised in that the output from the transmission is adapted to transfer drive to a differential located at the rear of the amphibious vehicle.
 2. A power train as claimed in claim 1, in which the differential is located reward of the engine.
 3. A power train as claimed in claim 1, in which the output from the power take off is in the form of an output shaft which is connected to a drive shaft which runs below or through the oil sump of the engine, or alongside the engine.
 4. A power train as claimed in claim 3, in which the sump has a tunnel or recess through which the drive shaft passes.
 5. A power train as claimed in claim 1, in which the marine propulsion unit is located in line with, or substantially in line with, the engine and the transmission.
 6. A power train as claimed in claim 1, in which the output from the transmission is transferred to the differential through a transfer case.
 7. A power train as claimed in claim 6, in which the transfer case is adapted to drive a further differential located toward the front of the vehicle for driving the front wheels of the vehicle.
 8. A power train as claimed in claim 1, in which a decoupler is provided such that drive to the marine propulsion unit can be selectively coupled and decoupled.
 9. A power train as claimed in claim 1, in which the engine is adapted to be mounted in the vehicle such that a crankshaft of the engine is substantially in alignment with the central longitudinal axis of the vehicle and with the front or timing end of the engine facing the rear of the vehicle.
 10. (canceled)
 11. An amphibious vehicle, characterized in that it comprises a power train as claimed in claim
 1. 